JP2017536262A - Process for manufacturing composite articles - Google Patents

Abstract

Epoxy resin formulations of liquid epoxy resins and mixtures of solid or semi-solid epoxy resins containing photoinitiators are cured or partially cured by radiation to avoid the need for thermal curing in the furnace Used as a matrix in a prepreg. The formulation is particularly useful in the manufacture of wind turbine blades, particularly in an automated process.

Description

  The present invention relates to a curable resin formulation that can be used as a matrix in the manufacture of fiber reinforced composites, and in particular, a resin that can be at least partially cured without the need to heat the prepreg in an oven to achieve a degree of cure. Concerning the formulation. The present invention also provides for the production of prepregs, the production of at least partially cured prepregs without the use of a furnace or autoclave, the partially cured prepreg itself, and the final results obtained from such prepregs in a fully cured state. It relates to the use of such resin formulations in articles.

  The term prepreg is used to describe a fibrous material embedded in a matrix of curable resin.

  Articles made from prepreg are becoming larger and more complex shapes. For example, prepregs are currently used in wind turbine blade manufacturing and aircraft fuselage, both of which are larger to meet modern demands. Traditionally, prepregs used in such production have included fibrous materials such as glass, carbon or aramid fibers embedded in a matrix of thermosetting resin. Typically, the article is made by laminating several layers of prepreg in a mold, which is heated in an oven to cure the resin blend.

  In these previous processes, the prepreg may be prepared before laminating the prepreg in the mold, or the fibrous material may be laminated dry in the mold and impregnated in the mold by resin injection. Good. Regardless of which technique is used for lamination, the resin formulation used as the matrix is thermosetting, typically a thermosetting resin such as an epoxy or polyester resin containing a heat-activated curing agent. including. As the size of the molded product increases, this not only requires a large mold, but also a large furnace to produce the final article, and a gradual to ensure sufficient and uniform heating of the laminated prepreg. A high heating rate. Therefore, the equipment cost increased.

  Cure of the thermosetting resin typically requires an accurate heating cycle to obtain the desired degree of cure of the resin throughout the prepreg or prepreg stack. The manufacture of large articles can require long curing times and / or high curing temperatures. This is difficult to achieve when using large convection-based furnaces and requires hard mechanical equipment. Furthermore, the thermosetting techniques currently used in the manufacture of these larger and / or complex shaped articles typically include manual prepreg lamination in a mold, which is time consuming. And labor, and can result in irregularities across the article.

  Lamination of large articles takes time and requires a lot of man-hours. Large articles also require a very long cure time to cure the resin while managing the release of exotherm, and sometimes the cure time can exceed several days. This limits the production rate of such articles and results in increased manufacturing costs associated therewith.

  Long curing times also mean that large articles that are cured in a conventional manner require a large amount of energy to produce. This is because the entire laminate is simultaneously heated until the entire article is cured using a much larger amount of energy than would otherwise be required to cure.

  In conventional processes, molds are occupied by lamination and curing, and as described above, these are long-running processes. The mold can only be reused when curing is complete, the article is removed, and the mold surface is ready to receive the next laminate. Thus, the only way to increase production speed using conventional lamination and curing methods is to invest in additional molds. Molds, especially molds adapted to withstand furnace curing temperatures, are expensive and represent a significant proportion of the cost of manufacturing large articles.

  US 2012/0138223 discloses the use of radiation curing of resin in a prepreg used in the manufacture of wind turbine blades. This discloses a multi-ply stack of prepregs to form a stack, which is then heated using infrared radiation and cured using ultraviolet radiation. If a thicker article is required, a subsequent stack may be built on top of the cured stack and cured as well. Such a process involves separate lamination and curing steps, which are time consuming. Furthermore, the bottom layer of the stack receives a lower proportion of IR and UV radiation than the top layer of the stack, which either has variable curing properties across the stack or sufficient radiation reaches the bottom layer. Means that excess energy is delivered to the upper layer. Thus, a process of this nature is inefficient in time and energy.

  The present invention aims to solve and / or generally provide improvements for any of the problems described above.

  According to the present invention there is provided a use, apparatus and process according to any one of the appended claims.

  The present invention further provides a resin in a prepreg comprising a liquid material and a solid epoxy resin, and a fibrous material impregnated with a resin blend, to allow at least partial curing of the prepreg without the use of a furnace. The use of a resin formulation comprising a mixture of photoinitiators for curing is provided.

  The present invention provides a resin formulation that can be used in the manufacture of large articles from a prepreg without the need for a large furnace to provide at least initial curing of a stack of prepregs.

  Resin blends that can be cured by means other than heat are known, and in particular, it is known that resin blends can be cured by radiation such as ultraviolet light. However, we find that the use of resin blends such as the present invention as a matrix in a prepreg avoids the need for large furnaces, especially in the manufacture of large articles such as wind turbine blades and aircraft fuselage parts. In addition, it has been found that automated lamination and curing of prepregs can be made possible.

  In one aspect of the invention, a process is provided for the production of partially or fully cured composite articles. A process comprising depositing individual layers of prepreg on a mold surface or other layers of prepreg. Heat and a second form of radiation are applied to the prepreg during and / or immediately after deposition to at least partially cure the deposited prepreg.

  In one aspect of the invention, an automated tape laminating apparatus for automated deposition and simultaneous partial curing of a prepreg is provided that includes a consolidation device, a heat source, and a second radiation source. Apparatus suitable for use with the prepreg and process of the present invention.

  In one aspect of the invention, a prepreg that includes a resin and a fibrous material impregnated with the resin and is at least partially curable without using a furnace, the resin comprising a liquid epoxy resin, a solid epoxy resin, and There is provided a prepreg further comprising a mixture of at least one radical initiator, preferably a photoinitiator, and optionally a radical (photo) curing accelerator. The prepreg is suitable for use with the automated tape laminator and process of the present invention.

  In a preferred embodiment of the present invention, prepreg deposition is performed by an automatic tape lamination (ATL) or automatic fiber placement (AFP) apparatus. This ensures a uniform and reproducible installation of the prepreg with highly aligned fiber reinforcements. This, on the other hand, results in the manufacture of articles with improved mechanical properties. It is envisioned that other known lamination methods such as filament winding are compatible with the present invention.

  In one aspect of the present invention, a process for producing a partially or fully cured composite article is provided, and when deposited, the prepreg is heated by an infrared (IR) or heat source to provide a second radiation source. Be exposed. Both the heat and the second radiation source initiate curing of the prepreg deposited layer. It is also preferred that any sub-layer of the prepreg where the deposited prepreg is placed is also heated to ensure good integration between subsequent layers. Preferably, the second radiation and / or thermal radiation also penetrates the lower prepreg layer to further cure the lower prepreg. Thus, the top and bottom layers of the prepreg are at least partially simultaneously cured during the deposition of the top layer of the prepreg. This ensures good integration between the layers and improves the interlaminar shear strength between the plies.

  Heat and / or the second radiation may be applied before, during or immediately after the prepreg. Preferably, heat or IR radiation is applied prior to deposition to achieve good adhesion to assist deposition, reduce resin viscosity and increase resin flow, and reduce prepreg viscosity to improve integration. It is added to the front side and / or the back side of the prepreg. Preferably, the prepreg sublayer is also preheated to increase its tack before deposition of the prepreg layer on the sublayer.

  The temperature of the deposited prepreg may be in the range of 20 to 90 ° C, preferably 30 to 80 ° C, more preferably 40 to 70 ° C, and most preferably 40 to 55 ° C. At these temperatures, the photoinitiator accelerates the curing of the prepreg, resulting in an overall optimized cure, and the green strength of the prepreg is greater than when the prepreg is cured using heat or a photoinitiator alone. Even faster is achieved. When the temperature is increased beyond the above range, the curing of the prepreg is fully controlled by the temperature, which does not lead to a reduction in the time to cure the prepreg to green strength.

  In one embodiment of the invention, pressure is applied to the front side of the prepreg as the prepreg is deposited. This may be applied by a consolidation device such as a shoe or roller, for example, when the prepreg is deposited using an AFP or ATL apparatus. Application of pressure during deposition further integrates the prepreg layer into the lower layer and reduces porosity by extruding voids from the interlayer region. Preferably, the consolidation device is attached to the deposition apparatus and operated simultaneously. Preferably, the consolidation device also provides heat to the prepreg.

  In a preferred embodiment of the present invention, a single ply length of prepreg is deposited by ATL or AFP moving across the mold surface. Once these plies are deposited, a heat, infrared or other radiation source equipped on or near the ATL device will at least partially cure it when the prepreg is deposited. Since the deposition and partial curing occur in the same process, the entire stack does not require heating or limited heating, which results in energy savings. This also ensures that the lengths of the prepregs in the stack are subjected to the same degree of curing, ensuring uniform characteristics across the final cured part.

  In a preferred embodiment of the invention, the prepreg is deposited and partially cured until the laminate achieves sufficient strength to be removed from the mold. At this point, the stack can be transferred to a furnace for complete curing with reduced energy, while another stack is deposited in the mold. This increases the production rate that can be obtained from a single mold.

  Another advantage of the present invention is that the mold does not need to be configured to withstand high furnace temperatures because heat and a second radiation source are applied directly to the prepreg as it is deposited. Therefore, a mold at a lower temperature can be used, and the mold cost can be greatly reduced.

  A vacuum bag prepreg or injected fiber causes a certain amount of resin to ooze out of the structure during curing. This means that the shape of the final article is different from the shape of the laminate. This change introduces internal stress and creates difficulties when trying to manufacture the article accurately. The present invention overcomes this when the prepreg is deposited as it is at least partially cured and does not cause resin leaching. Thus, the volume of the laminate according to the present invention exhibits minimal shape change during curing, and articles made as the present invention retain a near net shape.

  In one embodiment of the invention, the prepreg is deposited and the combined effect of the heating and integrated device used for the next coating layer of the prepreg causes the sub-layer of the prepreg to move from the location where it was deposited. It is sufficiently partially cured by heat and radiation from the device to such an extent that it does not move. In order to achieve this, it is necessary to provide a fast-curing matrix.

  Preferably, the deposited prepreg is at least partially cured by the apparatus to achieve “green strength” to the extent of at least 50%, preferably 80% (measured by differential scanning calorimetry (DSC)). The term is a term used to describe a composite structure having at least sufficient strength to be removed from a mold. Methods of determining the heat of reaction and cure rate, and the level or extent of cure using DSC, are described in the paper Heat of reaction, degree of cure, and vision of Hercules 3501-6 resin, Lee WI et al. , J Composite Materials, Vol. 16, p150, November 1982.

  In order for the process to achieve an improved production rate, the rate of prepreg deposition and at least partial curing is at least 5 mm / sec, preferably 10 mm / sec, more preferably 25 mm / sec or 50 mm / sec. There is a need. Preferably, it is at least 150 mm / second, more preferably at least 250 mm / second.

  In a preferred embodiment of the invention, the prepreg contains two or more UV photoinitiated curing agents each initiated by different wavelengths. Preferably, the prepreg has at least two photoinitiators. The use of two or more photoinitiated curing agents allows for an increased cure rate and greater control over the cure rate by applying different frequencies of radiation at different times. In an alternative embodiment, the apparatus of the present invention comprises a radiation source capable of providing multiple peak wavelengths of radiation. Alternatively, an array of different radiation sources with different peak wavelengths.

  The prepreg or resin formulation may include one or more photoinitiators that may be selected from sulfonium salts, which may include alkyl sulfonium salts, alkyl iodonium salts, fluorophosphates and / or fluoroantimonates. Photoinitiators are triarylsulfonium hexafluoroantimonate, diaryliodonium hexafluoroantimonate, diaryliodonium hexaflurolanmonate, triarylsulfonium hexafluorophosphate, triarylsulfonium BF4, triarylsulfonium hexafluorophosphate, diaryliodonium hexa It may be selected from fluorophosphates and / or salts of thioxanthone modified sulfonium. These salts may be present in a solvent that may be selected from propylene carbonate and glycidyl ether.

  The photoinitiator is 0.25 to 10 wt%, more preferably 0.4 to 8 wt%, even more preferably 0.5 to 6 wt%, even more preferably 0, based on the total weight of the formulation. Within the range of .75 to 5% by weight, or preferably 0.5 to 4% by weight, or preferably 0.9 to 3% by weight, or 1 to 2% by weight, or 1.5 to 2.5% by weight. And / or a combination of the above ranges.

  The prepreg or resin blend is composed of triethylene glycol divinyl ether, cyclohexane dimethanol, hydroxybutyl vinyl ether, cyclohexyl vinyl ether, trimethylolpropane oxetane, dendritic polyester polyol, polyether diol, polycaprolactone triol, aliphatic epoxy and dipentaerythritol pentane. One or more accelerators which may be selected from / hexaacrylate may further be included. We have found that each of these accelerators can enhance the curing of epoxy resin formulations containing at least one photoinitiator, particularly a photoinitiator as described in this application.

  The accelerator is from 0.25 to 10% by weight, more preferably from 0.4 to 8% by weight, even more preferably from 0.5 to 6% by weight, and even more preferably from 0.00%, based on the total weight of the formulation. Within the range of 75 to 5 wt%, or preferably 0.5 to 4 wt%, or preferably 0.9 to 3 wt%, or 1 to 2 wt%, or 1.5 to 2.5 wt%, And / or a combination of the above ranges.

  The fibrous material used with the resin blend used in the present invention may be carbon fiber, glass fiber or aramid tow, the tow being a strand composed of a plurality of fibers or filaments.

  The fibers or filaments used in the present invention may be glass and / or carbon fibers, with carbon fibers being particularly preferred in the manufacture of wind turbine shells longer than 40 meters, for example 50 to 60 meters. The tow is composed of a plurality of individual fibers and is preferably unidirectional. Typically, the tow has a circular or nearly circular cross section with a diameter in the range of 3 to 20 μm, preferably 5 to 12 μm. Different fibers may be used in the different prepregs used to produce the cured laminate.

  An exemplary tow is HexTow® carbon fiber available from Hexcel Corporation. Suitable HexTow® carbon fibers contain 6,000 or 12,000 filaments and are IM7 carbon fibers available as fibers having a weight of 0.223 g / m and 0.446 g / m, respectively; 12 IM8-IM10 carbon fiber containing 1,000,000 filaments and available as fibers weighing 0.446 g / m to 0.324 g / m; and containing 12,000 filaments, weight 0.800 g / m AS7 carbon fiber available as a fiber. Other useful materials include Panex 35, Mitsubishi TRH50 or Toray T300, T700 or T800.

  The present invention is particularly useful in the manufacture of wind turbine blades. As the size of wind turbine blades increases, their manufacturers require a multi-layer stack of composite fibers and resin reinforcement. Conventionally, resin impregnated fiber reinforcement (prepreg) is laminated in a mold to form these stacks.

  The resin used in the present invention is a mixture of liquid and solid epoxy resins. The solid epoxy resin may be solid or may be known in the art as a semi-solid. The reactivity of an epoxy resin is indicated by its epoxy equivalent (EEW), and the lower the EEW, the higher the reactivity. The epoxy equivalent weight can be calculated as follows: (epoxy resin molecular weight) / (number of epoxy groups per molecule). Another approach is to calculate an epoxy number that can be defined as follows: epoxy number = 100 / epoxy equivalent. To calculate the epoxy groups per molecule: (epoxy value x molecular weight) / 100. To calculate the molecular weight: (100 × epoxy groups per molecule) / epoxy value. To calculate molecular weight: Epoxy equivalent x epoxy groups per molecule.

  The liquid epoxy resin used in the present invention preferably has a high reactivity as indicated by an EEW in the range of 50 to 500, preferably a high reactivity such as EEW in the range of 50 to 250, and is a solid epoxy. The resin preferably has an EEW in the range of 300 to 1500. The resin composition includes an epoxy resin mixture and a photoinitiator, optionally with an accelerator. The solid / semi-solid and liquid epoxy resins are selected from monofunctional, bifunctional, trifunctional, tetrafunctional epoxy resins, and / or any epoxy resin having two or more functionalities. A blend of epoxy resins may be included.

  Suitable bifunctional epoxy resins include, by way of example, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A (optionally brominated), phenol and cresol epoxy novolac, glycidyl ether of phenol-aldehyde adduct, Aliphatic diol glycidyl ether, diglycidyl ether, diethylene glycol diglycidyl ether, aromatic epoxy resin, aliphatic polyglycidyl ether, epoxidized olefin, brominated resin, aromatic glycidyl amine, heterocyclic glycidyl imidine and amide, glycidyl Including those based on ethers, fluorinated epoxy resins, glycidyl esters or any combination thereof.

  The bifunctional epoxy resin may be selected from diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A, diglycidyl dihydroxynaphthalene, or any combination thereof.

  Suitable trifunctional epoxy resins include, by way of example, phenol and cresol epoxy novolacs, glycidyl ethers of phenol-aldehyde adducts, aromatic epoxy resins, aliphatic triglycidyl ethers, dialiphatic triglycidyl ethers, aliphatic polyglycidyl amines. , Heterocyclic glycidyl imidines and amides, glycidyl ethers, fluorinated epoxy resins, or any combination thereof. Suitable trifunctional epoxy resins are available from Huntsman Advanced Materials (Monthey, Switzerland) under the trade names MY0500 and MY0510 (triglycidyl para-aminophenol) and MY0600 and MY0610 (triglycidyl meta-aminophenol). . Triglycidyl meta-aminophenol is also available from Sumitomo Chemical Co., Ltd. (Osaka, Japan) under the trade name ELM-120.

  A suitable tetrafunctional epoxy resin is N, N, N ′, N′-tetraglycidyl-m-xylenediamine (commercially available from Mitsubishi Gas Chemical Company under the name Tetrad-X and from CVC Chemicals as Erysys GA-240. As well as N, N, N ′, N′-tetraglycidylmethylenedianiline (eg, MY0720 and MY0721 from Huntsman Advanced Materials). Other suitable multifunctional epoxy resins include DEN 438 (from Dow Chemicals (Midland, MI)), DEN 439 (from Dow Chemicals), Araldite ECN 1273 (from Huntsman Advanced Materials), and Araldite ECvantMandan (Mandland ECN1299). .

  We find that a mixture of semi-solid epoxy resin mixed with a liquid resin is particularly suitable, especially when the prepreg is automatically laminated and the viscosity of the prepreg is important to allow easy lamination of the prepreg I found.

  Pre-pregs are typically used in a different location from where they are manufactured, and therefore they require ease of handling. Therefore, it is preferable that the prepreg is dry or as dry as possible and has low surface tackiness. Therefore, it is preferable to use a high viscosity resin. This also has the advantage of slow impregnation of the fiber layer, allowing air to escape and minimizing void formation. Further, the prepreg may be partially cured by photoinitiation at one location and transferred to another location to complete the cure.

  The photoinitiator in the formulation used according to the present invention is selected according to the nature of the curable resin used in the formulation. We have particularly useful photoinitiation where alkylsulfonium salts such as CPI 6975 supplied by Estech Inc can be used to impart at least partial cure to the epoxy resin in the prepreg when subjected to ultraviolet light. It was found to be an agent. We have found that 0.2 to 10 wt%, preferably 3 to 8 wt%, more preferably 4 to 6 wt% of photoinitiator based on the weight of the resin formulation should be used. The formulation may also contain a catalyst for a photoinitiator, such as the product UV9390 offered by Momentive under the trade name of Silfone. We have found that the use of 10 to 30%, preferably 15 to 25% by weight of catalyst based on the weight of photoinitiator is particularly suitable.

  In addition to the photoinitiator, the resin formulation may contain a heat-activatable curing agent that can be activated after partial curing that can be provided by photoactivation of the photoinitiator. Thus, the prepreg may be laminated in a mold that is subjected to photoinitiation to effect partial curing of the resin, and then final curing is achieved by heating the partially cured prepreg. Also good. Final heat curing may be accomplished in conjunction with photocuring or may be accomplished at a separate location.

  The prepreg may be preferentially designed, for example, by doping with a compound or element that has an absorption or reaction property that increases with the specific radiation wavelength or wavelength range emitted by a pulsed or non-pulsed radiation source. . As a further example, the composite material may be coated with a surface layer of an alternative material that preferentially absorbs or reflects a particular wavelength or wavelength range emitted by a pulsed radiation source.

  In an automated process using the resin formulation according to the present invention, the prepreg can be fed to the mold by ATL or AFP equipment. An ATL or AFP apparatus typically comprises an automated robotic arm or gantry that supports a head capable of depositing a strip of prepreg of a particular length on a surface. For example, an ATL or AFP device may have a head with a chute that is fed with a pre-cut piece of prepreg or cut to a length by the device, which chute is then a piece of prepreg Can be guided under a compaction roller that can adhere the prepreg to the substrate, and the robot then passes through an array that provides radiation and / or heat, typically by moving an automated head. The prepreg can be pulled out.

  In other embodiments, the array may not be held by a head that stacks tows. For example, the array may be held by, but not limited to, different robot arms or other configurations that ensure proper heating of the heating area is achieved. Additionally or alternatively, the system may have a bed on which a tool or a previously laminated layer of composite material rests, the bed being configured to move relative to a stationary head. Alternatively, each of the head and the bed may be configured to move relative to each other, for example, along the same movement axis (for example, the X axis). In other words, embodiments of the present invention, in general terms, are not limited, and are configured to move relative to each other by any suitable means. Configuration) and tool or previously laminated layers of composite material (or layers laminated on the tool or previously laminated layers).

  The array may provide IR, UV, electron beam, microwave or radio frequency to induce or promote curing. Preferably UV radiation is used, more preferably radiation having a wavelength between 350 and 440 nm, or more preferably still 360 to 400 nm, most preferably 365 to 395 nm. The radiation source provides partial curing of the prepreg when it adheres to the tool or previous ply. The robot may have a shoe that can be heated, and once partial curing is achieved, the robot head continues to move in the direction of the X or Y axis, or a combination thereof, stacked and partially cured. Prepreg can be integrated.

  The array may comprise a single flashlight / sunlight or multiple flashlights / sunlights configured, for example, in a two-dimensional or three-dimensional configuration. The array may be mounted on a gantry or robot arm on the mold. If there are multiple flashlights and they provide pulsed radiation or heat, they are substantially simultaneously (i.e., simultaneously with each other, depending on the production rate being used, and the desired heating and cooling profiles), or It can be controlled to shine at substantially the same time) or with a time difference (eg alternately). Alternatively, each of the plurality of flashlights may have an independent control system and be configured to illuminate when it is necessary to achieve a predetermined heating profile on a previously laminated layer or mold contact surface. Good. Such a configuration can be used, for example, in the process of the present invention in which layers of prepreg are laminated as part of AFP, ATL or other automated system. In this (and in all other embodiments), the distance between the array and the heated contact surface can be controlled along the second axis (Y-axis), thereby increasing control over heating. .

  In alternative embodiments (not illustrated herein), the array may be mounted below the contact surface in addition to or instead of being heated. For example, to increase adhesion on both sides prior to deposition, for example by constructing an array above and below (or more generally on both sides) of one or more layers of composite material forming a composite structure In addition, it is possible to heat both contact surfaces substantially simultaneously. This configuration can find utility, for example, in systems where new layers or tows are laminated on both sides of an existing composite structure substantially simultaneously. Furthermore, the use of arrays to heat both sides of an existing composite structure can be employed to heat the bulk material more quickly and uniformly. This can be desirable, for example, in thermoforming applications. The array can also be used to heat the deposited prepreg to increase tack before subsequent layers are deposited thereon.

  The prepreg includes both fiber and matrix component materials. Each of these components can absorb and generate heat differently for a given wavelength range. Such completely different non-uniform heating characteristics may be undesirable in some scenarios. According to some embodiments of the invention, a heat source is selected that has a plurality of output radiation peaks that substantially correspond to the respective radiation absorption peaks of the component materials. In this way, each of the component materials can be heated according to a similar heating profile (ie, temperature increase over time). This can achieve a more consistent and efficient heating profile of the prepreg as a whole. In other embodiments, it has a relatively flat (eg, substantially continuous) emission spectrum that includes the respective radiation absorption peaks of the component materials, thereby providing an equally efficient heating profile for each component material A flashlight is selected that has

  Multi-axis panels mimicking materials such as unidirectional laminates and Hexcel products LBB1200 (0 °, 0 °, + 45 °, -45 °) have been produced with UV light initiation and are subjected to a series of tests, For example, DMA is used to establish the cure Tg of the material. Samples show E '(or loss modulus measured using DMA (Dynamic Mechanical Analysis)), Tg between 90-120 ° C does not require any post cure.

  The process of the present invention is highly tunable and many possible parameters that can be modified provide improved automated control over properties, product shape, and fiber orientation. Parameters including shoe temperature, shoe pressure, compaction roller temperature, UV lamp distance from the prepreg, robot operating speed, and the number of additional passes of UV light that allow final and complete curing are the properties of the prepreg, And may vary according to the nature of the final article to be manufactured.

  When the article undergoes final thermal curing, the epoxy resin composition may also include one or a conventional non-radiation activated curing agent. These include aliphatic or aromatic amines or their respective adducts, amidoamines, polyamides, alicyclic amines, anhydrides, polycarboxylic acid polyesters, isocyanates, phenolic resins (eg phenol or cresol novolac resins, copolymers, eg Phenol terpenes, polyvinylphenols or copolymers of bisphenol-A formaldehyde copolymers, bishydroxyphenylalkanes, etc.), dihydrazides, sulfonamides, sulfones such as diaminodiphenyl sulfones, anhydrides, mercaptans, imidazoles, ureas, tertiary amines, BF3 complexes, Alternatively, it can be selected from a mixture thereof. Particularly preferred curing agents include modified and unmodified polyamines or polyamides such as triethylenetetramine, diethylenetriaminetetraethylenepentamine, cyanoguanidine, dicyandiamide and the like. Particularly preferred curing agents are those encapsulated to prevent them from having a toxic effect on cationic curing by radiation initiated curing agents, and one such example of a particularly suitable encapsulated curing agent is: TEP (1,1,2,2-tetrakis (p-hydroxyphenyl) ethane).

  0.5 to 10% by weight based on the weight of the epoxy resin, more preferably 1 to 8% by weight, more preferably 2 to 8% by weight, more preferably 0.5 to 5% by weight, more preferably 0.5%. It is preferred to use from 1 to 4% by weight (including these values), or most preferably from 1.3 to 4% by weight (including these values) of the curing agent.

  If used, the urea curing agent may comprise a bisurea curing agent, such as 2,4 toluenebisdimethylurea or 2,6 toluenebisdimethylurea and / or a combination of the above curing agents. Urea-based curing agents may also be referred to as “uron”.

  A preferred urea-based material is a series of materials available under the trade name DYHARD®, a trademark of Alzchem, urea derivatives containing bisureas such as UR500 and UR505.

  When used, the heat-activated curing agent is preferably an onset temperature in the range of 115 to 125 ° C. and / or a peak temperature in the range of 140 to 150 ° C. and in the range of 80 to 120 J / g. Should have enthalpy (Tonset, Tpeak, onset temperature is defined as the temperature at which resin curing occurs during differential scanning calorimetry (DSC) scanning, while peak temperature is the resin temperature during (DSC) scanning Peak temperatures during cure, typically these are measured by DSC according to ISO 11357 at temperatures of -40 to 270 ° C. at 10 ° C./min).

  In one embodiment of the present invention, the heat source and the second radiation source may be provided by the same device. In alternative embodiments, both the heat and the second radiation source may be provided as continuous or pulsed radiation.

  The heat or radiation source according to embodiments of the present invention may use a pulsed electromagnetic radiation source (or simply “pulsed radiation source”). As will be described, some embodiments of the present invention use commonly known types of xenon flashlights, which may include one or more of IR, visible and ultraviolet (UV) light components. Can emit a relatively broad emission spectrum. Unless otherwise specified, the terms “flash” and “pulse” are used interchangeably herein, at least in connection with flashlight embodiments. However, in general, any other suitable pulsed or non-pulsed radiation source may be used according to alternative embodiments of the present invention. For example, according to some embodiments, a pulsed laser source may be used.

  As used herein, a flashlamp is a type of arc lamp designed to provide a short pulse (or flash) of high energy incoherent radiation having a relatively broad spectral component. Flashlights are used in photographic applications and in several scientific, industrial and medical applications. Using a pulsed radiation system rather than a continuous heating system has opened up several new options for controlling the heating temperature, as described herein. For the heating of the contact surface herein, the process adjusts one or more of several system parameters including, but not limited to, pulse number, pulse width (or flash duration), pulse intensity, and pulse frequency. Can be optimized. As described, molded or 3D reflectors can be used to collect emitted radiation and control its direction. The optimal 3D reflector may have a flat single curved surface or a double curved surface.

  Xenon flashlights are particularly suitable for use as a heat source according to the present invention, which can heat a contact surface of, for example, a composite material sample very quickly, consistently and controllably, typically Exceeds the performance of other heat sources such as known IR heat sources. In addition, after the pulse, the gas cools relatively quickly, i.e. maintains a lower residual heat (after switch-off) than the filament heater, which means that the flashlight is in operation compared to the filament heater. Provides much greater control over heating and cooling rates, meaning that the auxiliary heating and cooling subsystems taught in the prior art can be completely eliminated. This greater heating and cooling control capability can also help increase production rates, for example, thereby increasing the relative speed between the heater and the contact surface being heated.

  Successive pulses (flash) can be used to raise the surface temperature of a layer of prepreg (or any other contact surface, such as a tool) in a very controlled manner. The temperature can be controlled, for example, according to the number of pulses and the time between pulses, which in the illustrative example shown is one pulse about every 5 seconds. Of course, depending on the heating profile required, higher and lower pulse frequencies may be used. Once the surface reaches the target temperature, the time between pulses can be increased to maintain the desired temperature. Of course, other pulse parameters such as pulse intensity may be modified instead of or in addition to the pulse frequency to control and maintain the target temperature.

  Multiple pulses can be used to achieve and then maintain the target temperature. The combination of rapid heating (during the pulse) and relatively slow cooling (between the pulses) provides a novel method of temperature control during the manufacture of the composite article. For example, according to embodiments of the present invention, surface temperature varies between higher peaks and lower cooling areas, so surface heating and surface bonding can be targeted to target the optimum temperature of the process. The time difference between can be changed. As a result, surface temperature peaks can be utilized without having to heat the bulk of the material to its elevated temperature.

  In a further alternative embodiment of the present invention, a plurality of flash lamps (or other radiation sources) are mounted and configured to heat both unstacked and previously stacked layers of prepreg substantially simultaneously. May be. Of course, alternatively or in addition, one or more flashlights (or other radiation sources) may be mounted and configured to heat any other element or surface of the system as needed. Good.

  The radiation source output can be controlled according to the required head speed, i.e., the speed at which the head moves across the tool or previously laminated tows, to reach and maintain the target temperature and degree of cure. In particular, as the head speed increases, the radiation output increases as well (or vice versa). Additionally or alternatively, the degree of heating and curing can be controlled by changing at least one of the distance of the source (s) from the contact surface and the angle of incident radiation relative to the surface of the prepreg. In addition (or alternatively), a radiation filter may be placed between the source and the contact surface. Such a filter may be formed as part of the source itself or as an intermediate structure between the source and the heated contact surface.

  A preferred UV source is a UV LEDS that provides radiation with a wavelength between 340 and 430 nm. Exemplary UV sources include Phoseon® Fireline LED UV lamps and Heraeus Noblelight Fusion UV F300s. Preferred wavelengths can be selected from 365 nm and 395 nm.

  The structural fibers used in the prepreg may be in the form of randomly knitted non-woven multiaxial fibers, or any other suitable pattern. For structural applications, it is generally preferred that the fibers have a unidirectional orientation. If a unidirectional fiber layer is used, the fiber orientation can vary throughout the prepreg stack. However, this is simply one of many possible orientations of a stack of unidirectional fiber layers. For example, the unidirectional fibers in adjacent layers may be configured orthogonally to each other in a so-called 0/90 configuration (which indicates the angle between adjacent fiber layers). Of course, among many other configurations, other configurations such as 0 / + 45 / −45 / 90 are possible.

  Structural fibers may include broken (ie, checkout), selectively discontinuous or continuous fibers. Structural fibers can be formed from a wide variety of materials such as carbon, graphite, glass, metallized polymers, aramids and mixtures thereof. Glass and carbon fibers are preferred, and carbon fibers are preferred for wind turbine shells longer than 40 meters, for example 50 to 60 meters long. The structural fiber may be an individual tow composed of a plurality of individual fibers, and may be a woven fabric or a non-woven fabric. The fibers may be unidirectional, bi-directional or multi-directional depending on the properties required in the final laminate. Typically, the fibers have a circular or nearly circular cross section with a diameter in the range of 3 to 20 μm, preferably 5 to 12 μm. Different fibers may be used in the different prepregs used to produce the cured laminate.

  The structural fiber of the prepreg is substantially impregnated with an epoxy resin, and the prepreg has a resin content of 20 to 45% by weight, preferably 28 to 40% by weight, more preferably 30 to 38% by weight, based on the total prepreg weight. Have.

  After curing, the stack becomes a composite laminate suitable for use in structural applications such as automobiles, marine vessels or aerospace structures or wind turbine structures such as wing shells or spars. Such composite laminates may comprise structural fibers at a level of 80% to 15% by volume, preferably 58% to 65% by volume.

  The present invention has applicability in the manufacture of a wide range of materials. One specific use is in the manufacture of wind turbine blades. A typical wind turbine blade includes two long shells that join together to form the outer surface of the blade, and a support spar in the blade that extends at least partially over the length of the blade. The length and shape of the shell varies, but the trend is to use longer wings (requires longer shells), which, on the other hand, is the thicker shell and the material in the stack to be cured. Special arrangements may be required. This imposes special requirements on the material from which the wing is prepared. Carbon fiber based prepregs are suitable for wings with a length of 30 meters or more, in particular wings of 40 meters or more, for example 45 to 65 meters in length, while the dry fibers are preferably glass fibers. The length and shape of the shell can also lead to the use of different prepreg / dry fiber materials in the stack from which the shell is manufactured, and the use of different prepreg / dry fiber combinations along the length of the shell May lead to

  The invention will now be described by way of example only and with reference to the following examples.

The following formulations were prepared:

  The formulation was mixed in a 10 L Winkworth mixer and then filmed into two 65 gsm films, which were then impregnated into Ahlstrom R344 glass fibers having a net fiber air weight of 300 gsm. The prepreg was cut to size and then cured.

The curing process used a Fanuc Mi16B / 20 robot and the robot head was equipped with a chute that was fed with a pre-cut prepreg. This chute guided the prepreg under a compacting roller that adheres the prepreg to the substrate, and then moved the robot head to pull the prepreg through the UV array. The UV array provided 395 nm UV radiation with an intensity of 15 W / cm ² measured using a Dymax LED / UV radiometer. This UV source allowed partial curing of the prepreg at a cure rate of about 15 mm / sec (which is equal to 2.3 kg / hr).

  The panel was manufactured by laminating a plurality of piles in an arbitrary direction.

  The panel was also subjected to microscopic analysis for porosity. The porosity of the laminate of the present invention was less than 1%, which is compatible with current manual lamination processes.

  The robot was set to move at a speed of 15 mm / sec, and a 10 ply thick unidirectional panel with a Fanuc Mi16B / 20 at a shoe temperature of 200 ° C., a shoe pressure of 5 bar, 100% UV intensity (395 nm). When used and subjected to an ILSS (interlaminar shear strength) test (according to ASTM EN2563), values of more than 30 MPa were obtained.

  Set the robot to move at a speed of 15 mm / sec, use a 10-ply thick unidirectional panel with a shoe temperature of 200 ° C., a shoe integrated pressure of 5 bar, and 100% UV intensity (395 nm) for curing. When used and subjected to an interlaminar shear strength test, values greater than 30 MPa were obtained. Triaxial “like” panels were also tested for ILSS, yielding an average value of 39.1 MPa, and when the panel was also tested for flexural strength and flexural modulus, average values of 660 MPa and 28 GPa were obtained, respectively. These results show that the properties of the experimental photocured material are close to the strength of a commercial system produced by thermosetting in a furnace.

Example 6
In this example, the components are as follows:
LY1589 Bisphenol A epoxy resin (Huntsman)
TASHFP triarylsulfonium hexafluorophosphate (50% by weight in solution in propylene carbonate)
TASHFA triarylsulfonium hexafluoroantimonate (50% by weight in solution in propylene carbonate)

The formulation was prepared using the following formulation.

Papers Heat of reaction, degree of cure, and vision of Hercules 3501-6 resin, Lee WI et al. , J Composite Materials, Vol. 16, p150, November 1982, these formulations were used in differential scanning calorimetry (DSC, PerkinElmer DSC6000) to measure the heat of reaction and rate of cure, as well as the level or extent of cure. ) And dielectric analysis (DEA, using Nietzsch DEA 288 Epsilon). In addition, the glass transition temperature (T _g ) according to ASTM E1356, and enthalpy and transition temperatures were determined according to ASTM 3418 and ASTM E2038 and E2039.

The results are shown in Table 2 below.

  The formulation of Example 6c provides an advantageous 80% cure time of 0.4 minutes, while the maximum rate of cure allows thermal management of exothermic emissions in laminates containing multiple prepreg layers. It was a desirable level to do.

The formulation of Example 6c was used to impregnate 2400 tex fiber tow and a unidirectional glass fiber reinforcement material weighing 600 g / m ² . A laminate was prepared from 4 layers of this prepreg material.

The laminate was subjected to the following cure schedule. Each formulation was heated to 50 ° C. and the light source produced light with a wavelength of 365 nm with an output of 8 W / cm ² . The material was exposed to the light source at various speeds of 5 mm / sec, 12.5 mm / sec, 25 mm / sec, 37.5 mm / sec and 50 mm / sec. It has been found that the laminate can be fully cured for processing speeds up to 25 mm / sec in a single pass.

Claims (26)

A process for manufacturing a composite article,
a) depositing a prepreg containing a radiation-initiated curing agent on a mold using an automated device;
b) applying heat and second source radiation to at least partially cure the prepreg simultaneously with the deposition of the prepreg.   The process of claim 1, wherein the radiation-initiated curing agent comprises at least two initiators configured to be initiated with different frequencies of radiation.   The process of claim 1, wherein the second radiation is ultraviolet light.   4. A process according to any one of claims 1 to 3, wherein heat is applied using an infrared lamp or a xenon bulb.   5. A process according to any one of the preceding claims, wherein pressure is applied to the prepreg by the automated device during deposition.   The process of any one of claims 1 to 5, wherein the composite article is partially cured and then removed from the mold.   The process of claim 6, comprising the additional step of completing in-furnace curing of the composite article removed from the mold.   A process according to any one of the preceding claims for the manufacture of wind turbine blades.   A prepreg comprising a resin and a fibrous material impregnated with said resin, at least partially curable without using a furnace, said resin being a liquid epoxy resin, a solid epoxy resin, and at least one radical initiation A prepreg further comprising an agent, preferably a photoinitiator, and optionally a mixture of radical (photo) curing accelerators.   The prepreg of claim 9, wherein the resin further comprises an encapsulated amine curing agent.   11. A prepreg according to claim 9 or 10, wherein the fibrous material used with the resin blend is carbon fiber, glass fiber or aramid tow.   The prepreg according to any one of claims 9 to 11, wherein the fiber or filament is glass and / or carbon fiber.   The prepreg according to any one of claims 9 to 12, wherein the liquid epoxy resin has an EEW in the range of 50 to 500.   The prepreg according to any one of claims 9 to 13, wherein the solid epoxy resin has an EEW in the range of 500 to 1500.   The prepreg according to any one of claims 9 to 14, wherein the solid epoxy resin is a semi-solid epoxy resin.   16. A prepreg according to any one of claims 9 to 15, wherein the photoinitiator is selected from sulfonium salts comprising alkyl sulfonium salts, alkyl iodonium salts, fluorophosphates and / or fluoroantimonates.   The photoinitiator is 0.25 to 10% by weight, preferably 0.5 to 6% by weight, more preferably 1 to 4% by weight, even more preferably 1.5%, based on the weight of the resin formulation. The prepreg according to any one of the preceding claims, present in an amount of from 3 to 3% and / or a combination of the above ranges.   The prepreg according to any one of claims 1 to 17, wherein the resin blend contains a heat-activatable curing agent such as polycyandiamide, urea-based curing agent or imidazole.   The prepreg according to any one of the preceding claims, wherein the resin formulation contains an accelerator that can be selected from:   An automated tape laminating apparatus for automated deposition and simultaneous partial curing of a prepreg, comprising an consolidation device, a heat source, and a second radiation source.   The automated tape laminating apparatus of claim 19, wherein the second radiation source is an ultraviolet light source.   21. The automated tape laminator of claim 19 or 20, wherein the ultraviolet light source comprises an array of sources configured to provide ultraviolet light to at least two target frequencies.   The automated tape laminating apparatus according to any one of claims 19 to 21, wherein the consolidation device comprises a heating shoe.   Use of a prepreg according to any one of claims 9 to 18 by a process according to any one of claims 1 to 8.   23. Use of an automated tape laminating device according to any one of claims 19 to 22 by a process according to any one of claims 1 to 8. Use of a prepreg according to any one of claims 9 to 18 by a process according to any one of claims 1 to 8.